The present invention relates to semiconductor devices using a photoresist, and to processes for manufacturing the same.
Various types of photoresists have been used or proposed. These resists should have a variety of desirable characteristics or properties. In general, all or most of these resists generally demand etching resistance, adhesiveness with low light absorption at 193 nm wavelength for ArF. Additionally, the resists should be developable by using 2.38 wt % aqueous tetramethylammonium hydroxide (TMAH) solution. It is, however, difficult to synthesize a polymer satisfying one or all these properties.
Many researches have focused on studies on norbolac type resin as a resin to increase transparency at 193 nm wavelength and increase etching resistance. As merely an example, "Bell Labs" tried to introduce alicyclic unit to the backbone chain of a copolymer in order to enhance etching resistance. A copolymer resin in which the backbone chain has norbornene, acrylate and maleic anhydride substituent, as represented by chemical formula I has been suggested:
[FORMULA I] See Appendix A
In the polymer resin of formula I, the maleic anhydride portion (portion A) was used for polymerizing alicyclic olefin group.
The maleic anhydride portion is soluble in 2.38% aqueous TMAH solution even it is not exposed, and thus a y-portion having tert-butyl substituent should be highly increased in order to prevent dissolution. But increase of the y-portion causes relative decrease of z portion, which enhances sensitivity and adhesiveness with substrate, to cause disadvantage in that photoresist is removed from the wafer in practical patterning.
Thus, an effective pattern cannot be formed without separately using a solubility controlling agent, and even if a pattern is formed by using a solubility controlling agent, the adhesiveness is too poor to be applied to practical patterning.
Under such circumstances, Bell Labs tried to solve the above-mentioned problems by using a solubility controlling agent of cholesterol type and by employing two-component resist comprising a polymer of cyclo-olefin and maleic anhydride.
However, in this case, very large amount (about 30% by weight based on the polymer) of the solubility controlling agent should be used, and thus the polymer of the above molecular structure basically has too low reproducibility and too high cost to be used as a polymer for a photoresist. From the above, it is seen that an improved photoresist resin that is cost effective, easy to manufacture, and has desirable other properties is clearly desired.